An important role for the oxidation of low density lipoproteins (LDL) in atherogenesis is strongly supported by expanding knowledge on cellular effects of oxidized LDL, evidence for oxidized LDL in vivo, and inhibition of atherogenesis in WHHL rabbits by the antioxidant drug probucol. Despite this progress, the chenistry of lipid and protein alterations in oxidized LDL has been defined only in a general and most nonspecific manner, and specific chemical correlations with cellular effects are lacking. The commonly measured thiobarbituric acid reactive substances (TBARS) represent a nonspecific assay of aldehydic reaction products that account for only 1-2% of total lipid peroxidation products in oxidized LDL. We have used chemically specific methods based on high presure liquid chromatography and gas chromaography/mass spectroscopy to identify hydroperoxy and hydroxy derivatives of linoleic and arachidonic acids as the predominant species of fatty acid oxidation products on oxidized LDL. This application proposes comparative studies of the chemistry of LDL oxidation under various experimental conditions and studies of the relationship between cellular effects and specific oxidation chemistry. For copper-catalyzed oxidation of LDL, we shall determine formation of cysteine sulfonic acid, location of cleavage sites in apolipoprotein B, time course of lipid and protein alterations related to vitamin E disappearance, and the generation of oxidized species, as well as hydrolysis of ester bonds, among lipid classes, focussing especially on phospholipid hydrolysis. LDL oxidized by endothelial cells, macrophages, and smooth muscle cells will be assessed similarly and compared to copper-oxidized LDL. The role of cell-derived lipid hydroperoxides or other diffusable oxidants in initiating LDL oxidation will be determined. Parameters important in potential LDL oxidation in vivo will be determined in a fluid-filled wound chamber in rabbit subcutaneous tissue. Key cellular effects of oxidized LDL-monocyte adherence to endothelium and cytotoxicity-will be correlated with presence of specific lipid peroxidation products in oxidized LDL,and the ability of these products to transger between lipoprotein species will be determined. The ability of oxidized LDL to cause measurale cellular oxidant stress, possible by transfer of lipid hydroperoxides to cells, will be determined. These studies will fill a broad gap in our knowledge of the chemistry of oxidized LDL generation and its effects, and will form an esssential basis for the understanding of its role in atherogenesis.